1. Field of the Invention
The present invention relates to a method of converting input video signals to have a desired resolution and an apparatus using the same, and more particularly, to a method of converting a resolution of video signals, by which the details of the input video may be provided in high definition without additional definition enhancement circuits, such as a peaking circuit, by filtering video signals with optimal filter coefficients being calculated based on a resolution of input and output video signals, and an apparatus using the same.
2. Description of the Related Art
Since digital display devices, such as a liquid crystal display (LCD), a digital micro-mirror device (DMD), and a plasma display panel (PDP), have a display resolution fixed for each product model, a video input to the individual digital display device has different resolutions, and thus, should be converted to have a resolution adjusted to a corresponding display device.
Particularly, a resolution conversion technique is required to convert a variety of digital television formats, defined by the advanced television system committee (ATSC), into a format which may be reproduced in a high definition television (HDTV).
The resolution conversion techniques allow for the converting of a sampling rate of an input video signal, and the conversion techniques are classified into a resolution extension to convert a low-resolution format into a high definition format and a resolution reduction to convert a high-resolution format into a low-resolution format. In the case of the resolution extension, since new signal components are interpolated between samples of an original input signal, a blurring takes place due to losses of high frequency components when the signals are being filtered. Therefore, users can readily recognize a deterioration of display quality when standard definition (SD) video signals are reproduced on a high definition digital display device, such as the HDTV.
Also, in the case of the resolution reduction, since high frequency components in an input video are aliased on a low frequency signal, deterioration, such as a zigzag artifact and a moiré pattern, occurs.
According to conventional linear filtering techniques as disclosed in U.S. Pat. No. 5,889,895 and U.S. Pat. No. 5,671,298, resolution conversion is accomplished by using a bilinear interpolation and a cubic interpolation. However, since high frequency components of the input video are not sufficiently extended during the resolution extension, both the definition and the display quality deteriorate. To compensate for such a problem, a method was proposed in which a peaking is applied to a low resolution video to identify potential edge pixels, and then edge pixel detection, edge linking, and luminance transition enhancement are sequentially accomplished so as to output high definition video signals. However, such a scaling method uses a conventional linear filter, and thus, has a problem that both pre-processing and post-processing require an increase in arithmetic operations and additional hardware, thus causing costs to increase because the peaking and the luminance transition enhancement should be accomplished for the video signals in both pre-processing and post-processing stages during filtering to improve the display quality and the definition of a video.
In addition, according to the conventional art disclosed in U.S. Pat. No. 5,852,470 and U.S. Pat. No. 5,446,804, video signals corresponding to the edge regions are processed satisfactorily. However, fine textured regions of a video cannot be processed with high definition. In addition, their performances are unsatisfactory compared to the linear filtering technique, with the exception of most regions of the edge components.